There is a stereoscopic image generation apparatus which generates an image which can be stereoscopically viewed by using parallax of images captured by two adjacent cameras. The stereoscopic image generation apparatus, for example, generates and displays the image captured by the one camera among the images captured by the two adjacent cameras as a left-eye image and the image captured by the other camera as a right-eye image.
A difference in the positions of the left-eye image and the right-eye image of the same object is referred to as parallax. Since parallax amount of two objects exist in an image are different from each other, the one object seems to exist in front of or in back of the other object according to the parallax amount. The parallax amount is a magnitude of the parallax.
FIG. 32 is a diagram illustrating an example of a stereoscopic image. In FIG. 32, an image 910 is a left-eye image, and an image 920 is a right-eye image. Herein, in each of the images 910 and 920 as left-eye and right-eye images, an object A, an object B, and an object C exist. Due to the parallax of these objects between the images 910 and 920, with respect to a person viewing the stereoscopic image of FIG. 32, these objects seem to exist in the order of the object A, the object B, and the object C from the front side.    [Patent Literature 1] Japanese Laid-open Patent Publication No. 2005-176004    [Patent Literature 2] Japanese Laid-open Patent Publication No. 2008-66086    [Patent Literature 3] Japanese Laid-open Patent Publication No. 2007-041425    [Patent Literature 4] Japanese Laid-open Patent Publication No. 06-301033    [Patent Literature 5] Japanese Laid-open Patent Publication No. 2000-98119    [Patent Literature 6] Japanese Laid-open Patent Publication No. 04-035192    [Non-Patent Literature 1] Glossary of Display Apparatus, Japan Electronics and Information Technology Industries Association
In addition, in a stereoscopic image generation apparatus where a lenticular lens sheet is installed on a display device such as a liquid crystal display, right and left eyes are allowed to recognize different images without dedicated glasses.
FIG. 33 is a schematic plan diagram illustrating a structure of a stereoscopic image generation apparatus using a lens sheet in the related art. In an example illustrated in FIG. 33, a user (viewer) 903 is positioned in front of a stereoscopic image generation apparatus 900 in the related art where a lens sheet 902 is installed on a liquid crystal display 901.
The distance A from the viewer 903 to the lens sheet 902 in the vicinity of a central portion 902a of the liquid crystal display 901 is different from the distance B from the viewer 903 in front of the apparatus to the lens sheet 902 in the vicinity of a peripheral portion 902b of the liquid crystal display 901.
At the position in front of the stereoscopic image generation apparatus 900 in the related art, an image in the vicinity of the central portion 902a of the liquid crystal display 901 can be recognized as a stereoscopic image. However, when the user 903 turns (rotates) the head around the top TP of the head in the left or right direction to view the vicinity of the peripheral portion 902b, since the distances to the lens sheet 902 (liquid crystal display 901) are different, the images are blurred, so that the images cannot be recognized as a stereoscopic image.
The imaging distance (focal length) of the lens sheet of the stereoscopic image display apparatus in the related art will be described with reference to FIG. 34. First, a focal length of a general convex lens satisfies the following Equation (1).1/f=(n−1)(1/R1−1/R2)+(n−1)×(n−1)/n×t/R1R2  (1)where,f: focal lengthn: refractive index of lensR1: ratio of curvature viewed from the pixel sideR2: ratio of curvature viewed from the viewer sidet: thickness of lens
Herein, since the plano convex lens has a semicylindrical shape, R2 has an infinite value, and thus, “1/R2” becomes zero.
In addition, similarly, since R2 has an infinite value, “t/R1R2” also becomes zero. Therefore, the above Equation (1) is expressed as follows.1/f=(n−1)(1/R1)
In addition, herein, n is a fixed value according to a material of the lens. Therefore, f is determined depending on R1.
Since the distance from the lens to the viewer is “a”, the focal length, that is, the position where the R, G, and B pixels form an image is f=a.
Therefore, the position where the viewer can form a 3D image is f, and the value of f is determined based on R1. In addition, R1 depends on the distance b from the pixel to the lens.
However, in the stereoscopic image generation apparatus 900 in the related art illustrated in FIG. 33, the distance b between the liquid crystal display 901 and the lens sheet 902 is constant, and thus, in order to control the image forming position of the 3D image, a ratio of curvature of each lens of the lens sheet 902 needs to be appropriately changed.
However, a pixel pitch of a general liquid crystal display is about 0.418 mm, and thus, in order to produce a lens sheet having a lens array with this accuracy, the lens forming accuracy needs to be in the order of 10−8 mm.
Therefore, the method of producing the lens sheet 902 by finely changing the ratio of curvature of the lens is difficult and impractical in terms of the lens forming accuracy.